It has been observed in varactor voltage controlled oscillator circuits that sideband noise (SBN) varies with the current and varactor tuning voltage of the oscillating device. For each tuning voltage of a VCO (for a given varactor capacitor and Q) there is an optimal VCO bias current that minimizes SBN. However, conventional VCOs used in phase locked loops suffer SBN performance degradation, as the tuning voltage varies, because in present circuits the VCO bias current is fixed. Therefore, a need exists for VCOs that are able to automatically adjust the bias current to compensate for SBN degradation caused by tuning voltage change.